As the range of applications of wireless power transmission technology has expanded, various attempts to improve efficiency of a power amplifier have been conducted, central among them being envelope tracking (ET) technology, using active voltage control.
In an output terminal of an envelope tracker integrated circuit (ET IC) for implementing envelope tracking (ET), generally, a power inductor and a bead, in addition to a multilayer ceramic capacitor, have been used so as to prevent high-frequency noise (50 MHz or more, for example, 80 to 130 MHz) from being transferred to the power amplifier at the time of operation, while serving to supply power to the power amplifier.
Meanwhile, in accordance with the recent trend for the miniaturization of electronic products, there is an attempt to provide a coil component capable of simultaneously performing functions of the power inductor and the bead disposed in the output terminal of the envelope tracker integrated circuit (ET IC). However, in view of the fact that in a small coil component, a self resonant frequency (SRF) is formed in an excessively high frequency region, it has been difficult to implement a coil component as described above without changing a type of magnetic material or a shape of electrodes.